Spring counterbalance



Aug. 1, 1939. I w HAUPT 2,168,209

SPRING COUNTERBALANCE Filed July 16, 1937 INVENTOR ZZZ BY f ATTORNEYPatented Aug. 1, 1939 2,168,209

UNITED STATES PATENT OFFICE SPRING COUNTERBALANCE Walter H. Haupt,Ludlow, Ky., assignor to The Kelley-Koett Manufacturing Company, Inc.,Covington, Ky., a corporation of Ohio Application July 16, 1937, SerialNo. 154,047 s Claims. (01. 248123) This invention relates to acounterbalancing plate I! and a lower end plate l8 between which systemfor 'X-ray apparatus, ultra-violet lamps, and into which are mounted aplurality of heliand the like. cal springs l9. If desired, only onespring may Among the objects of this invention is the probe used, but inthe case where heavy weights have vision of such a system in whichweights are subto be balanced, a plurality is recommended be- 5stitutedby springs. Ordinarily a weight and a cause many small springsare cheaper than one spring are regarded as mechanical equivalents largeone and by leaving ofi one or adding one and no invention is deemed toreside in their a closer approximation of the weight to the interchange.It has long been desired however, spring tension can be had. Failureof-one spring 10 to replace the heavy weights necessary to balance alsowill not allow the weight to fall if a plurality 10 heavy shockproofX-ray heads which contain of springs are used. transformers and oil andfrequently weigh over a On bottom end plate l8, a second cable l3a, ishundred pounds. The problem is not merely to attached in a non-slidablemanner by means of balance such a head at a given point on a 001- acentral eye bolt 20 and then the cable continues umn or standard but tobalance it statically at down the column, as will be explained. The up-15 any point on the column While making the head D end p e which isStationary during the easy to move and balance throughout the heightcounterbalancing operation, is adjustable for of the column. If such anarrangement is suce and consequent y for Spring tension by a cessful,the saving in weight can be utilized to vertical screw 2!. Turning a nut22 which is make the column and base stifier and stronger. integral withthe screw and located above cap 20 The ti saving in weight of course,need not I5 is sufiicient to accomplish the adjustment since benullified by making the rest of the apparatus the screw is threaded inplate I! but unthreaded heavier. where it passed thru cap 15. A springguide 23 is It is well known that helical springs do not also provided nt e co to p the Springs 251 require equal work to make them contract orfrom twisting when the tension is increased by 25 expand equal distancesat all times. The more turnin nut the spring is already compressed, thegreater the Inverted on the upper part of base I0 and relative amount ofwork necessary to make it within it is a pulley 24 of peculiar shape. Itis still shorter. The more it is already stretched, so mounted as to befreely rotatable on an axle 30.: the greater the relative amount of workto make boss .25 which is attached rigidly to the inner 3 it stretchstill further. If such a spring is used side of base II]. The upper endof the pulley is in a balancing arrangement to act upon a congroovedwith sheaves, but'is generally cylindrical, stant weight, there will bemore or less cable to but the lower end is grooved with sheaves of atake up, depending upon the leverage exerted by rapidly decreasingspiral form. The distance of 5; the weight. The means provided fortaking up this spiral from its axis 25 is proportional to the 5 andpaying out cable while changing the leverage increase in work performedas the springs I9 are thereupon are an essential part of my invention.stressed from minimum tension, at which they In the drawing, Fig. l is avertical section of are when carriage I2 is at its uppermost posianX-ray standard showing the spring and take tion on the column, to aposition of maximum up arrangement. tension which they occupy whencarriage I2 is 40 Fig. 2 is a plan view of the top of the column as fardown the column'as to be in contact with showing the pulley arrangement.shoulder 26 of base Ill. It is believed that a Fig. 3 is a cross sectionof the column taken sp r l f s h approximately Such q ckness along theline 3-3 of Fig. 1. is knownin mechanics as the fusee spiral al- 4 is aplan view of the spiral pulley as tho absolutely definite information onthis point 45 seen from below. is not at hand. In the drawing, [0 is thebase of the apparatus Another way o expressing this at on s t while IIis the column. I2 is the X-ray head say that t product of e sp n tensi ntimes and carriage (shown only in part) to be balanced. the axialdistance of the acting point on the spi- It encircles the column. Acable l3 extends from r l gr v i designed to be a on nt and efiec- 50 Ycarriage l2 over a pulley l4 mounted obliquely tively equal to theproduct of the load being as shown in Fig. 2 on the top of the column,balanced times the radial distance of the effective which is a cap 15.radius on the cylindrical part of 24.

Within the column ll, there is a spring as- A third way of expressingthis would be to say sembly l6, which is made up of an upper end that asthe spring tension increases the pull of 5 the springs is applied closerto center and becomes less effective as rapidly as the pull increases soas to have a constant efiect. This constant eifect permits the load tobe balanced at rest at any point on the column. When the pull of thesprings I9 is greatest, its efiective lever arm on the pulley is least,therefore, no greater pull is exerted than when the lever arm is greaterbut the pulling force less.

The upper part of pulley 24 is cylindrical so that cable !3 may have aconstant point of application. This cable comes down the column afterleaving pulley l4, passes unattached thru the spring assembly and thenturns toward pulley 24 after leaving a pulley 2'! at the base of thecolumn. It is wrapped around the cylindrical portion of pulley 24sufiiciently to allow full traverse of the carriage l2 on the column.Cable I3 is then anchored at its pulley end to a point on thecylindrical part of pulley 24, as shown in Fig. 4.

The second cable, l3a runs from the eyebolt 29 around the pulley 28 atthe base of the column, thence to and about the spiral portion of pulley24. At the top point of the spiral it is anchored as Fig. 4 shows. Thearrangement is such that cable l3a reaches the apex of the spiral andspring assembly 16 is stretched to its greatest tension when carriage I2is at its lowermost point.

To operate my counterbalancing system it is merely necessary to lift ordepress carriage l2 slightly and to cease applying force when thecarriage has attained the desired position. Downward motion of thecarriage pulls end plate I8 down by exerting a pull on cable l3 wrappedon pulley 24, causing the pulley to rotate and Wrap up the cable with acontinuously decreasing lever arm. The action may be likened to that ofa bicycle going up hill, the drive sprocket continually decreasing insize as the hill grows steeperso that the effort required to turn thepedals stays constant. Lifting the carriage merely reverses the process.

I claim as my invention- 1. In an apparatus comprising a column and acarriage to be counterbalanced on said column and a base supporting saidcolumn and carriage, a plurality of helical springs vertically arrangedinside the column, a pair of end plates to which the ends of saidsprings are attached, the lower part of the assembly being movable, acombination pulley comprising a spirally grooved portion and a coaxialcylindrical portion, said pulley being rotatably mounted on the base, acable connecting the lower end of the spring assembly with the spiralgroove of the said pulley and a second cable connecting the carriage tothe cylindrical part of said pulley, the spiral grooves on the face ofthe pulley being adapted to guide the second cable so as to keep thecounterbalancing force of the spring assembly exerted upon the carriagethrough said first cable, a constant.

2. In an apparatus comprisng a column and a carriage to becounterbalanced on said column, a hollow base supporting said column andcarriage, a plurality of helical springs vertically arranged within saidcolumn, a pair of end plates to which said springs are attached, thelower part of the assembly being vertically movable within the column,screw means for vertically adjusting the height of the upper one of saidplates, a combination pulley comprising a spirally grooved portion and acoaxial cylindrical portion, said pulley being rotatably mounted on thebase, a cable connecting the lower end of the spring assembly with thespiral groove of the said pulley and a second cable connecting thecarriage to the cylindrical part of said pulley, the spiral grooves onthe face of the pulley being adapted to guide the second cable so as tokeep the counterbalancing force of the spring assembly exerted upon thecarriage through said first cable, a constant.

3. An apparatus according to claim 2 in which the construction of thespiral pulley is such that as the tension of the springs increase, theeffective lever arm of the cable on the pulley, by which the pull of thesprings is exerted, becomes less in the same proportion.

4. In an X-ray standard or the like, a base, a column arising from saidbase, a carriage movable on said column, a plurality of helical springswithin saidcolumn, end plates to which said springs are anchored, thelower part of the assembly being vertically movable within the column,means for holding rigid the upper one of said end plates, a pulley atthe top of said column, pair of pulleys at the bottom of said column, aspiral pulley in said base, a cylindrical portion on said pulley, acable extending from the said carriage over the first pulleyunattachedly down said column, around one of said lower pulleys thenceto and about the cylindrical.

part of said spiral pulley, where it is fastened, a second cableattached to and extending about said spiral pulley back to the other ofthe pulleys at the base of said column and thence to the lower end platewhere it is tightly fastened.

5. An apparatus according to claim 4 in which the spiral pulley hasgrooves which run in a fusee spiral. v

6. In an X-ray apparatus or the like, a hollow base, a column arisingtherefrom, a carriage movable on said column, a plurality of helicalsprings vertically arranged within said column, a pair of end plates towhich the ends of said springs are attached, the lower part of theassembly being vertically movable within the column, a cap on saidcolumn, a screw running thru.

said cap and the upper one of said end plates, a pulley mounted on saidcap, a pair of pulleys at the base of said column, an inverted spiralpulley rotatably mounted Within the base, said pulley having acylindrical section, and a cable extending from said carriage over saidfirst pulley down the column, around one of said pulleys at the base ofsaid column, then to and about the cylindrical section of said spiralpulley, a second cable extending about a spiral path on said pulleythence around the second of the pulleys at the base of said column'andfinally being attache to the lower one of said end plates.

'7. An apparatus according to claim 6 in which. the spiral path of saidspiral pulley is at such distances from the axis of rotation of saidpulley that the product of the spring tension times the axial distanceof the acting point on the spiral is a constant eilectively equal to theproduct of the load being balanced times the radial distance of theeffective radius on the cylindrical part of said pulley.

8. In a counterweight balancing device, a vertical column, a carriagemovable along said column, a pulley having combined cylindrical andspirally grooved co-axial portions, acable joining said pulley andcarriageso as to effect a rotary movement of the said pulley as a'conse-.

quence of the movement of the carriage caused by a pull on the cablewhich is joined to the cylindrical portion of said pulley, a helicalspring assembly within said column, said assembly comprising an upperrigidly held plate, a lower vertically movable plate and a plurality ofhelical springs each attached by one of its ends to one of said plates,a second cable joining the lower one of said plates with the spiralportion of said pulley, the proportions of the pulley cable and springbeing such in relation to each other that when the spring assembly isstretched to its maximum by reason of a position of said carriage, thelever arm of the second cable on the pulley, tending to produce rotationthereof, is at 5 its maximum.

WALTER H. HAUPT.

